Hi cgs,
How long can you go at +160km/h?
What happens then?
Have you tried to test the Turbo valves/Pop-off/Blow-off funktion?
Do you have the possibilities to read out the Motormanagements selfdiagnosis?
If you tell me some more about ya probs I`ll try to help you with some suggestions. 
By the way, it is not possible to switch off the Turbo in any way. 
